The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Known vehicle powertrain systems include one or more torque actuators coupled to transmissions that transfer torque to a driveline for tractive effort. Known torque actuators include internal combustion engines and electric motor/generators. Known powertrain systems employing electric motor/generators may have high-voltage and low-voltage electrical systems. Known electrical systems transform high-voltage electric power generated by an electric motor/generator to low-voltage DC electric power using an inverter and auxiliary DC/DC power module. Elements of high-voltage electrical systems may be disabled under specific circumstances.
Known electrical systems operate in low-voltage electric power generating modes using control strategies that include operating auxiliary DC/DC power modules at constant electric power output at a fixed voltage setpoint. Low-voltage electric power generating modes may include operating the engine at idle speeds and generating electric power with the low-voltage electrical system to provide low-voltage electric power for operating auxiliary vehicle systems. When engine speed drops below a trigger point, a control system may execute a load shedding scheme to avoid engine stalling. Known load shedding schemes may frequently engage due to engine speed sags associated with vehicle/engine deceleration and associated return to idle operation. Known systems experience rapid engine speed increase subsequent to triggering a load shedding event, which may create a surge in driveline torque.
A known powertrain system employing an electric motor/generator includes a belt-alternator-starter (BAS) system as a torque actuator in place of an alternator. Known BAS systems include a serpentine belt to transfer torque between the engine and the electric motor/generator. Known BAS systems use a high-voltage energy storage system supplying high-voltage electrical power through a voltage inverter to the motor/generator unit. Known BAS systems use a low-voltage electrical system to provide low-voltage electric power for operating auxiliary vehicle systems such as headlamps, interior lights, entertainment systems, power seats, electric windows and HVAC components.